Apparent "speed" of the moon versus nearby stars

Got into a discussion with someone recently about recommended shutter speeds to avoid motion blur of the moon. He was adamant that the moon moves much faster than stars do. I cannot understand that. Its orbit is in the same direction as the Earth is rotating, and takes about 29 days, so, in theory, it should "move" about 1/29th slower than stars that are near it.

Am I missing something here?

Sidereal tracking rate (15.041 arcseconds per second).

Lunar tracking rate (14.685 arcseconds per second).

Solar tracking rate (15.0 arcseconds per second).

The Moon traverses the entire 360 degree celestial sphere over a period of 28 days giving it a retrograde proper motion relative to the celestial sphere of about 1/2° per hour.

ChrisBeere said:

Sidereal tracking rate (15.041 arcseconds per second).

Lunar tracking rate (14.685 arcseconds per second).

Solar tracking rate (15.0 arcseconds per second).

The Moon traverses the entire 360 degree celestial sphere over a period of 28 days giving it a retrograde proper motion relative to the celestial sphere of about 1/2° per hour.

Click to expand...

Thanks. That's what I had thought. Well, he'll probably figure it out. Certainly easier to do that with digital cameras than with film.

SQLGuy said:

Got into a discussion with someone recently about recommended shutter speeds to avoid motion blur of the moon. He was adamant that the moon moves much faster than stars do. I cannot understand that. Its orbit is in the same direction as the Earth is rotating, and takes about 29 days, so, in theory, it should "move" about 1/29th slower than stars that are near it.

Am I missing something here?

Click to expand...

The Moon is orbiting the Earth in an approximate 28 day cycle. The stars and Sun do NOT orbit the Earth. All three (Moon, Sun, Stars) are moving across the Earth's sky at three different speeds. If you get lucky enough to do a time lapse video of the Moon near a bright star, you might actually catch it appearing to back over the star, which is called occulting. Here is a time lapse I captured of the Moon occulting Alderbaran back in 2016. So yes, the Moon appears to travel at a slower speed across the sky than do the nearby stars.

--
Best Regards,
Jack
YouTube channel: https://www.youtube.com/channel/UCAfQN-Ygh9z7qqUXdZWM-1Q
Flickr Meteor Album: https://www.flickr.com/photos/jackswinden/albums/72157710069567721
Sony RX100M3, a6000, and a7

W5JCK said:

SQLGuy said:

Got into a discussion with someone recently about recommended shutter speeds to avoid motion blur of the moon. He was adamant that the moon moves much faster than stars do. I cannot understand that. Its orbit is in the same direction as the Earth is rotating, and takes about 29 days, so, in theory, it should "move" about 1/29th slower than stars that are near it.

Am I missing something here?

Click to expand...

The Moon is orbiting the Earth in an approximate 28 day cycle. The stars and Sun do NOT orbit the Earth. All three (Moon, Sun, Stars) are moving across the Earth's sky at three different speeds. If you get lucky enough to do a time lapse video of the Moon near a bright star, you might actually catch it appearing to back over the star, which is called occulting. Here is a time lapse I captured of the Moon occulting Alderbaran back in 2016. So yes, the Moon appears to travel at a slower speed across the sky than do the nearby stars.

Click to expand...

Yes. I understand that. But that was not the other photographer's position. His statement was that the moon moved much faster (I am assuming, I think safely, from an Earth-based perspective) than the stars. He told me I should go aim a good long lens at it and I would see that the moon would move across the frame much faster than stars would.

The only other thing I can think of is that he was comparing the moon moving near the ecliptic relative to stars near the pole. But, even then, his idea that 1/125th was needed with a 500mm lens is clearly incorrect.

SQLGuy said:

W5JCK said:

SQLGuy said:

Got into a discussion with someone recently about recommended shutter speeds to avoid motion blur of the moon. He was adamant that the moon moves much faster than stars do. I cannot understand that. Its orbit is in the same direction as the Earth is rotating, and takes about 29 days, so, in theory, it should "move" about 1/29th slower than stars that are near it.

Am I missing something here?

Click to expand...

The Moon is orbiting the Earth in an approximate 28 day cycle. The stars and Sun do NOT orbit the Earth. All three (Moon, Sun, Stars) are moving across the Earth's sky at three different speeds. If you get lucky enough to do a time lapse video of the Moon near a bright star, you might actually catch it appearing to back over the star, which is called occulting. Here is a time lapse I captured of the Moon occulting Alderbaran back in 2016. So yes, the Moon appears to travel at a slower speed across the sky than do the nearby stars.

Click to expand...

Yes. I understand that. But that was not the other photographer's position. His statement was that the moon moved much faster (I am assuming, I think safely, from an Earth-based perspective) than the stars. He told me I should go aim a good long lens at it and I would see that the moon would move across the frame much faster than stars would.

The only other thing I can think of is that he was comparing the moon moving near the ecliptic relative to stars near the pole. But, even then, his idea that 1/125th was needed with a 500mm lens is clearly incorrect.

Click to expand...

Obviously you cannot grasp what we are telling you, and quite frankly, showing you via video. The Moon IS traveling a tiny bit slower across the sky than the stars nearby it, NOT faster. Show the guy the damn video and chill out.

W5JCK said:

SQLGuy said:

W5JCK said:

SQLGuy said:

Got into a discussion with someone recently about recommended shutter speeds to avoid motion blur of the moon. He was adamant that the moon moves much faster than stars do. I cannot understand that. Its orbit is in the same direction as the Earth is rotating, and takes about 29 days, so, in theory, it should "move" about 1/29th slower than stars that are near it.

Am I missing something here?

Click to expand...

The Moon is orbiting the Earth in an approximate 28 day cycle. The stars and Sun do NOT orbit the Earth. All three (Moon, Sun, Stars) are moving across the Earth's sky at three different speeds. If you get lucky enough to do a time lapse video of the Moon near a bright star, you might actually catch it appearing to back over the star, which is called occulting. Here is a time lapse I captured of the Moon occulting Alderbaran back in 2016. So yes, the Moon appears to travel at a slower speed across the sky than do the nearby stars.

Click to expand...

Yes. I understand that. But that was not the other photographer's position. His statement was that the moon moved much faster (I am assuming, I think safely, from an Earth-based perspective) than the stars. He told me I should go aim a good long lens at it and I would see that the moon would move across the frame much faster than stars would.

The only other thing I can think of is that he was comparing the moon moving near the ecliptic relative to stars near the pole. But, even then, his idea that 1/125th was needed with a 500mm lens is clearly incorrect.

Click to expand...

Obviously you cannot grasp what we are telling you, and quite frankly, showing you via video. The Moon IS traveling a tiny bit slower across the sky than the stars nearby it, NOT faster. Show the guy the damn video and chill out.

Click to expand...

Obviously you cannot grasp that agreeing with someone while acting like you're correcting them will tend to cause communications difficulties.

But, thanks for the video.

--
A7R4a with SEL2470Z, 55Z, and a number of adapted lenses (Canon FD, Minolta AF, Canon EF, Leica, Nikon...); A7R converted to IR.

W5JCK said:

SQLGuy said:

Got into a discussion with someone recently about recommended shutter speeds to avoid motion blur of the moon. He was adamant that the moon moves much faster than stars do. I cannot understand that. Its orbit is in the same direction as the Earth is rotating, and takes about 29 days, so, in theory, it should "move" about 1/29th slower than stars that are near it.

Am I missing something here?

Click to expand...

The Moon is orbiting the Earth in an approximate 28 day cycle. The stars and Sun do NOT orbit the Earth.

Click to expand...

OMG! This is sacrilege! I'm calling the Pope! :-D

W5JCK said:

All three (Moon, Sun, Stars) are moving across the Earth's sky at three different speeds. If you get lucky enough to do a time lapse video of the Moon near a bright star, you might actually catch it appearing to back over the star, which is called occulting. Here is a time lapse I captured of the Moon occulting Alderbaran back in 2016. So yes, the Moon appears to travel at a slower speed across the sky than do the nearby stars.

Click to expand...